Distribution: At the foot of the Andes in Argentina in the provinces of Jujuy, Salta, Tucuman, Catamarca, San Juan and Mendoza, and also in the provinces of Buenos Aires, Cordoba, San Luis, and Rio Negro; on the western side of the Andes in Chile from the province of Antofagasta to Colchagua. Oenothera picensis subsp. picensis isadv€titive on the Juan Fernandez Islahds and in the provinces of Bio-Bio and Malleco in southern Chile.
Habit: Annual herb with an erect or somewhat decumbent main stem, not forming a rosette, simple or branched near the base, 2-10 dm tall. Plants very densely to sparsely long-villous, the hairs soft, densely to sparsely short-villous and glandular-pubescent.
Leaves: Cauline leaves narrowly elliptic to lanceolate, acute, acute to truncate at the base, sessile, 3.5-10 cm long, 0.5-2 cm wide; bracts narrowly oblong or narrowly lanceolate to narrowly ovate, acute, truncate to subcordate at the base, sessile, 2.5-6 cm long, 0.5-2 cm wide, longer than the capsule they subtend or subequal to them, occasionally shorter; leaves plane or coarsely undulate at the margins, irregularly serrate, the teeth blunt.
Flowers: Inflorescence mostly branched, floral tube 1.5-4.5 cm long, buds oblong to lanceolate in outline, 0.7-1.7 cm long, 3-5 mm thick, often red striped at the junction of the sepals with the floral tube, sepals often flecked with dark red, apices of the sepals 1-2 mm long, mostly erect, petals broadly obovate to very broadly obovate, sometimes broadly elliptic, 0.7-2.5 cm long, anthers 5-12 mm long, filaments 5-15 mm long, style short, the anthers shedding pollen directly on the stigma at anthesis, 2-6 cm long, stigma lobes 3-6 mm long, ovary 1-2 cm long.
Fruit: Capsule (20-) 25-40 (-45) mm long, 3-4 mm thick.
Seeds: Seeds elliptic to broadly elliptic in outline, 1.2,-2 mm long, 0.5-0.8 mm thick, brown.
Chromosomes: Gametic chromosome number, n = 7 (ring of 14, ring of 10 and ring of 4 or ring of 8 and ring of 6 at meiotic metaphase I).
Notes: Self-pollinating complex heterozygote.